This invention relates to a process for decomposing hydroperoxides at elevated temperatures in the presence of a specific binary homogeneous catalyst comprised of chromium and ruthenium which is stable and exhibits improved activity, as well as selectivity for organic hydroperoxide decomposition to the desired alcohol and ketone products.
2. Description of the Prior Art
The decomposition of hydroperoxides catalyzed by transition metal complexes has been investigated for a number of years. It is generally assumed that in the first stage of decomposition, the hydroperoxide molecule forms an active complex with the metal catalyst. This complex decomposes subsequently into free radicals or molecular species which yield final products in further reactions.
In U.S. Pat. No. 3,879,467 there is disclosed a process for the catalytic oxidation of certain hydrocarbons utilizing an organic hydroperoxide in the presence of a chromium catalyst to produce alcohols and ketones as the primary products. Also disclosed in this patent for this purpose are a number of other specific metal catalysts which resulted in low hydroperoxide conversions or low product yields, or both, or in instances where high conversions were noted, almost no product yields were obtained.
In U.S. Pat. No. 3,925,316, a process is disclosed for the preparation of mixtures of cycloalkanols and cycloalkyl ketones by heating cycloalkyl hydroperoxides in the presence of, as catalyst, a soluble derivative of vanadium, molybdenum, or ruthenium.
Certain forms of ruthenium have also been reported in recent publications in connection with cumene hydroperoxide decomposition studies. In this regard, attention is directed to "Use of the Proton NMR Relaxation Method to Study the Coordination of Cumene Hydroperoxide With Cobalt and Ruthenium Carboxylates", V. M. Nekipelov, Dokl. Akad. Nauk SSSR, V 261 (6), 1377-81 (1981); "NMR Studies of .Mu3-Oxotriruthenium Hexacarboxylate Cumene Hydroperoxide Interaction", A. M. Trzeciak, Oxid. Commun., V. 1 (4), p. 295-303 (1980); and "Cumene Hydroperoxide Decomposition Reaction Catalyzed by Ruthenium (III) beta.-diketonates", A. M. Trzeciak, et al, React. Kinet. Catal. Lett., V. 12 (1-2), p. 121-5 (1981); and "Decomposition of Organic Hydroperoxides on Ruthenium .pi.-Complexes", Yu A. Aleksandrov, Ah. Obshch. Khim., V. 48 (9), p. 2142 (1978).
Binary homogeneous metal catalyst combinations previously disclosed for decomposition of specific hydroperoxides include the combination of a particular salt of iron and copper in U.S. Pat. No. 3,401,193, and an admixture comprised of cobalt and chromium compounds for effecting cyclohexane oxidation and decomposition of resultant hydroperoxide in U.S. Pat. No. 3,987,100.
The use of heterogeneous metal catalysts has also been disclosed in recently issued publications, for example, in U.S. Pat. No. 4,173,587, there is disclosed the use of a non-soluble rhenium compound for the decomposition of cumene hydroperoxide; in U.S. Pat. No. 4,209,465, there is disclosed the decomposition of cumene hydroperoxide by use of specified carbonium, tropylium or oxonium salts as catalysts; and in U.S. Pat. No. 4,059,598, there is disclosed the decomposition of residual hydroperoxides resulting from propylene epoxidation in the presence of a homogeneous cobalt oxide catalyst which may also contain copper oxide as a promoter.
However, prior art catalyst systems were deemed unsatisfactory in their ability to provide a stable catalyst system or lacked desired activity in the decomposition of hydroperoxide, or failed to provide the selectivity to the desired product(s). In an effort to correct one or more of these apparent deficiencies, the trend has been to employ stabilizing ligands in combination with certain metallic catalysts; however, many of these ligands are not readily available and are expensive to employ in any large quantity, especially on a commercial scale.